This invention relates generally to processor-based systems and particularly to such systems whose components may be swapped.
In a variety of circumstances, it may be desirable to swap or exchange components such as external memory cards in a processor-based systems. In some systems, different memory cards may be used to store different information or programs. In other cases, it may desirable to swap memory cards to repair or upgrade those memory cards.
Many processor-based systems include circuitry to enable hot swapping. With hot swapping, components such as memory cards may be removed while power is still applied to the processor-based system. In other words, the system does not need to go through a configuration cycle associated with the booting process in order to recognize newly inserted cards or other components.
While enabling hot swapping has many advantages, it also necessarily involves additional costs. Circuitry needs to be added to buffer the signals while the swapped component powers up. Moreover, circuitry needs to be provided to ensure that the component smoothly attaches to the rest of the processor-based system.
The extra expense of hot swap circuitry may be eliminated by making sure that the system is powered down when the component is swapped. For example, it may be necessary to ensure that the battery is removed from the processor-based system before swapping a component. The battery may be physically located in front of a swappable memory card. Then, the battery must be removed to swap the card.
The need for such an approach arises because many computer users are now fully apprised of hot swapping. They may be unaware or may have forgotten that a particular system does not support hot swapping. While in the past it may have been assumed that hot swapping was not possible, with the proliferation of systems that incorporate hot swapping, users may be prone to simply hot swap memory cards in systems that do not include this functionality.
The situation is made even more complicated in modern processor-based systems because the sources of power may be diverse. Power may be supplied, for example in portable processor-based systems, by both batteries and power carrying cables connected to the system. Examples of power carrying cables include buses that supply power such as the Universal Serial Bus (USB), and the Apple Desktop Bus (ADB) to mention two examples.
Thus, the user must appreciate that prior to swapping the memory card, not only must the battery be removed but also any power carrying cables must be removed. This adds a level of complexity that may be problematic for some users of processor-based systems.
Ideally, processor-based systems may operate like conventional consumer appliances. Many processor-based systems have the look and feel of conventional consumer-based appliances. Examples of appliance-like processor-based systems include digital audio players and digital cameras. Users may not appreciate that in fact the system is a processor-based system because it acts and feels like an appliance.
To require that the user understand the operation of the system sufficiently to know that, to replace the memory card, powered cables must be removed, reduces the appliance-like operation of the system. Moreover, the system may be damaged or may fail to operate correctly when users fail to take the required steps before replacing memory cards.
Thus, there is a need for a better way to avoid hot swapping circuitry in processor-based systems while still allowing components to be replaced.